The invention relates to a remote control system in which each of a plurality of remote control functions is represented by a message sequence comprising a plurality of binary bits of which a binary bit 0 and a binary bit 1 are distinguishable from each other by having, for the whole duration of a first period, different time ratios of two different parameters, being respectively a high level and a low level portion of a bit period, forming a pulse duration signal having an edge each time said signal is changing from one level to the other.
In most remote control system used nowadays for controlling a television receiver, an ultrasonic beam is used as the carrier for transmitting information from the transmitter to the receiver.
However such ultrasonic transmission is sensitive to disturbance because ultrasonic sound can easily be produced by moving certain objects present in the room where said remote control system is operating.
Therefore, newer systems use, instead of an ultrasonic beam, an infra red beam as the carrier for transmitting the information from transmitter to receiver.
However certain TV setmakers are still using the older ultrasonic method while others use the infra red beam.
Thus, the manufacturer, of the encoder for the transmitter and the decoder for the receiver, which decoder and encoder are nowadays manufactured as integrated circuits made on a semi-conductor body, has to take care that they can be used for both systems.
It should also be taken into account that the light emitting diodes (LED), used as the light source at the transmitter end, require a relatively large current in order to emit sufficient infra red light to reach the receiving channel in the TV receiver, which can be situated at several meters distance from the transmitter.